Low-cost particulate matter (PM) sensors offer high potentials in air quality monitoring. Their performance, however, strongly depends upon the materials used, their design and on the sampling and operational conditions. In this work we evaluate the performance of the latest Alphasense PM sensors under real-life outdoor and indoor conditions. Our observations highlight differences in the accuracy of these sensors, especially when sampling aerosol particles that have different properties from those used for calibration and under real-life conditions, but also high potentials for improvements.